1. Field of the Invention
The present invention relates to a resin film and a multilayer printed wiring board containing an insulating layer obtained by curing said resin film, which are used suitably for insulation of electric and electronic fields.
2. Description of the Related Art
In multilayer printed wiring board carrying electronic parts such as LSI, represented by a mounting substrate (interposer), metal wires are arranged not only on the multilayer printed wiring board surface but also inside thereof in three dimensions. Such a multilayer printed wiring board may have stress by repetition of expansion by generation of heat of LSI etc. at the time of energization, and contraction at the time of stopping energization, and by the change of external temperature environment. Due to the stress, cracks may be generated in insulating layer of cured epoxy resin, and metal wires in a multilayer printed wiring board may be cut, thus there have been a problem of low electric reliability.
In order to cope with the problem, it is proposed that a film of an epoxy resin compounded with a polyether sulfone is cured, and the cured product is used as the insulating layer of a multilayer printed wiring board for increasing the toughness of a insulating layer of a multilayer printed wiring board. Moreover, using a filler as one component of a resin film for lowering the thermal expansion coefficient of insulating layer is proposed (JP-A-2001-72834).
However, as the insulating layer obtained by curing such a resin film, further improvements of fire retardancy and metal plating processability are required.